1. Field of the Invention
The present invention relates to an internal combustion engine including: a valve system including a camshaft for opening and closing an engine valve provided in a cylinder head; and a breather system provided with a breather chamber into which blow-by gas flows from a crank chamber having a crankshaft housed therein.
2. Description of Background Art
An internal combustion engine with the following configuration has been known (see, for example, International Patent Publication No. WO 2005/005793).
Specifically, this internal combustion engine includes a valve system, a breather system, and a decompression system. The valve system includes a camshaft for opening and closing an engine valve. The breathe system is provided with a breather chamber into which blow-by gas flows through an introduction space communicating with a crank chamber having a crankshaft housed therein. The decompression system releases a compression pressure in a combustion chamber. In this internal combustion engine, the rotation of a member which is provided to the camshaft, and which forms the breather chamber, is utilized so that oil separated in the breather chamber can be caused to flow out of the breather chamber by a centrifugal force.
Suppose a case where, in a breather system, oil separated in a breather chamber is caused to flow out of the breather chamber by utilizing centrifugal force generated by the rotation of the camshaft of the valve system. In this case, if a rotating member which forms the breather chamber, and which rotates integrally with the camshaft is attached to the camshaft, the formation of the breather chamber leads to an increase in the number of components.
In addition, when the breather chamber is formed of the rotating member, blow-by gas flows into the breather chamber in a direction from the radially outer side to the radially inner side of the rotating member positioned radially outward of the camshaft. Hence, it is difficult to allow the blow-by gas to smoothly flow into the breather chamber.
Moreover, the blow-by gas which has flown into the breather chamber swirls in association with the rotation of the rotating member. Accordingly, if the distance over which the blow-by gas flows in the breather chamber is increased to accelerate the gas-liquid separation utilizing a centrifugal force (that is, separation of oil) in the axial direction of the camshaft, the size of the rotating member is increased in the axial direction. Hence, an engine body part (for example, a cylinder head) in which the camshaft is provided is increased in size in the axial direction. In addition, when multiple breather chambers are provided outside the camshaft and along the axial direction of the camshaft in order to enhance the gas-liquid separation function in the breather chambers, the engine body part is further increased in size in the axial direction.